Caplan takes a skeptical look at the tendency of today’s parents to ruin their own lives hoping that this might improve the future of their kids. In his book he reviews and evaluates the current literature on the nature/nurture question, especially twin- and adoption studies. And the results are often surprising.
The short conclusion of the book is, that parenting has a lot less long-term influence than you think and that it might be better to just enjoy your time with the kids, than to force them to activities that neither you nor your kids will enjoy.

In addition to an extensive literature review, Caplan also offers some interesting insight from the economists point of view. While researchers in the nature/nurture discussion often look at the facts and then decide, that there is no or little long term influence of the parents, Caplan takes a step back and asks “what if there is an influence, but it is equally likely to be positive or negative”. In other words, half of the kids stick to their parents advice and half of them rebel and do the exact opposite. This would not show up in the aggregate data. But when you consider your actions as a parent, you either have no influence or you run a serious risk of making things worse. Both cases aren’t desired outcomes, if you invest a lot of time in your child’s upbringing.
I also liked his emphasis on the point, that you are not only raising your kids, but also your future grandchildren, and that you should consider this long term consequence, when you are thinking about having a second (or third) child.

There are some points that I do not agree with, especially how he discards the limited nature of the earth’s resources and advocates more kids to solve a lot of problems. While I think that the predictions of the Club of Rome are probably exaggerated, the monetary prize of many resources currently does not account for scarcity due to political influences: I recently heard (I think in the economist, but I can not find the link at the moment) that current oil price does not include the value of the price of oil in the ground, but is simply based on the extraction cost. So the Arab leaders treat the oil like either an unlimited asset or more likely threat it as a common good leading to the tragedy of the commons. And having more kids will not adjust for this scarcity.

Despite these minor flaws I think, “selfish reasons to have more kids” is a great read for parent or those who ponder about having kids, even if you do not agree with Caplan’s political views.